During the past several years, environmental pollution concerns have led those active in the coatings, castings, and moldings industries to investigate various compositions in which organic solvents derived from petroleum have been eliminated or at least substantially reduced in quantity. Thus, compositions such as water-based compositions and high solids compositions have been extensively investigated. Even more recently the petroleum embargo and the resultant high cost and scarcity of petroleum by-products has increased interest in the investigation of compositions which are composed substantially of inorganic constituents.
The present invention relates to a curable composition composed substantially of inorganic constituents. More particularly, the present invention relates to curable compositions comprising aqueous solutions of water-soluble silicates and water-soluble latent insolubilizing agents.
A number of water-soluble silicate compounds are known in the art. Such compounds include sodium silicate, potassium silicate, lithium silicate and quaternary ammonium silicates which readily dissolve in water to form solutions therewith. Inasmuch as the pH of these solutions is normally higher than about 10.5, the silica will remain soluble therein. However, when these water-soluble silicates are blended with insolubilizing agents (i.e., crosslinkers) quite often the resultant solution is unstable. Thus, for example, the combination of water-soluble silicates with metal oxides of the form MO such as cadmium oxide, copper oxide, calcium oxide, lead oxide and the like has produced unstable systems in that these materials ordinarily cause precipitation of insoluble hydroxides or silicates of these oxides. In addition to problems of composition stability, films formed from water-soluble silicates and water-soluble insolubilizing agents have in the past proven to be extremely sensitive to water. Thus, such compositions have heretofore been deficient in wet abrasion resistance.
Accordingly, as will be apparent, a curable composition containing a water-soluble inorganic silicate and a water-soluble latent insolubilizing agent which exhibits excellent stability and produces cured products having excellent durability, stain resistance, resistance to heat and flame and water-resistance as well as other desirable properties is of considerable advantage.